Planetary gear train of automatic transmission for vehicle

ABSTRACT

Nine or more forward speeds and at least one reverse speed are achieved by a planetary gear train of an automatic transmission for a vehicle including an input shaft, an output shaft, three planetary gear sets respectively having four rotation elements, and six control elements for selectively interconnecting the rotation elements.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to and the benefit of KoreanPatent Application No. 10-2015-0171007 filed on Dec. 2, 2015, the entirecontents of which is incorporated herein for all purposes by thisreference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an automatic transmission for avehicle.

Description of Related Art

Recent increases in oil prices are triggering hard competition inenhancing fuel consumption of a vehicle.

In this sense, research on an engine has been undertaken to achieveweight reduction and to enhance fuel consumption by so-calleddownsizing, and research on an automatic transmission has been performedto simultaneously provide better drivability and fuel consumption byachieving more shift stages.

In order to achieve more shift stages for an automatic transmission, thenumber of parts is typically increased, which may deteriorateinstallability, production cost, weight, and/or power flow efficiency.

Therefore, in order to maximally enhance fuel consumption of anautomatic transmission having more shift stages, it is important forbetter efficiency to be derived by a smaller number of parts.

In this respect, an eight-speed automatic transmission has been recentlyintroduced, and a planetary gear train for an automatic transmissionenabling more shift stages is under investigation.

The information disclosed in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and should not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing aplanetary gear train of an automatic transmission for a vehicle havingadvantages of, by minimal complexity, realizing at least nine forwardspeeds and at least one reverse speed, thereby improving power deliveryperformance and fuel consumption due to multi-stages, and improvingdriving stability of a vehicle by utilizing a low rotation speed of anengine.

A planetary gear train according to an exemplary embodiment may includean input shaft for receiving an engine torque, an output shaft foroutputting a shifted torque, a first planetary gear set having first,second, and third rotational elements, a second planetary gear sethaving fourth, fifth, and sixth rotational elements, a third planetarygear set having seventh, eighth, and ninth rotational elements, a fourthplanetary gear set having tenth, eleventh, and twelfth rotationalelements, and six control elements for selectively interconnecting therotational elements and a transmission housing.

The planetary gear train according to an exemplary embodiment mayfurther include a first connecting member connected with the firstrotational element and directly connected with the transmission housing,a second connecting member connected with the second rotational elementand the fifth rotational element, and selectively connectable with thetransmission housing, a third connecting member connected with the thirdrotational element, and selectively connectable with the input shaft, afourth connecting member connected with the fourth rotational elementand directly connected with the input shaft, a fifth connecting memberconnected with the sixth rotational element and the ninth rotationalelement, and selectively connectable with the transmission housing, asixth connecting member connected with the seventh rotational elementand the tenth rotational element, and selectively connectable with theinput shaft, a seventh connecting member connected with the eighthrotational element and the twelfth rotational element, and selectivelyconnectable with the transmission housing, and an eighth connectingmember connected with the eleventh rotational element and directlyconnected with the output shaft.

The first planetary gear set may be a single pinion planetary gear set,where the first rotational element is a first sun gear, the secondrotational element is a first planet carrier, and the third rotationalelement is a first ring gear. The second planetary gear set may be asingle pinion planetary gear set, where the fourth rotational element isa second sun gear, the fifth rotational element is a second planetcarrier, and the sixth rotational element is a second ring gear. Thethird planetary gear set may be a single pinion planetary gear set,where the seventh rotational element is a third sun gear, the eighthrotational element is a third planet carrier, and the ninth rotationalelement is a third ring gear. The fourth planetary gear set may be asingle pinion planetary gear set, where the tenth rotational element isa fourth sun gear, the eleventh rotational element is a fourth planetcarrier, and the twelfth rotational element is a fourth ring gear.

The six control elements may include a first clutch selectivelyconnecting the input shaft and the third connecting member, a secondclutch selectively connecting the input shaft and the sixth connectingmember, a third clutch selectively connecting the input shaft and theseventh connecting member, a first brake selectively connecting thesecond connecting member and the transmission housing, a second brakeselectively connecting the fifth connecting member and the transmissionhousing, and a third brake selectively connecting the seventh connectingmember and the transmission housing.

Shift stages realized by selective operation of two control elements ofthe six control elements may include a first forward speed formed bysimultaneous operation of the first and third brakes, a second forwardspeed formed by simultaneous operation of the second clutch and thethird brake, a third forward speed formed by simultaneous operation ofthe second clutch and the first brake, a fourth forward speed formed bysimultaneous operation of the second clutch and the second brake, afifth forward speed formed by simultaneous operation of the first andsecond clutches, a sixth forward speed formed by simultaneous operationof the second and third clutches, a seventh forward speed formed bysimultaneous operation of the first and third clutches, an eighthforward speed formed by simultaneous operation of the third clutch andthe second brake, a ninth forward speed formed by simultaneous operationof the third clutch and the first brake, and a reverse speed formed bysimultaneous operation of the first clutch and the third brake.

A planetary gear train according to an exemplary embodiment of thepresent invention may realize at least nine forward speeds and at leastone reverse speed formed by operating the four planetary gear sets assimple planetary gear sets by controlling six control elements.

In addition, a planetary gear train according to an exemplary embodimentof the present invention may substantially improve driving stability byrealizing shift stages appropriate for rotation speed of an engine dueto multi-stages of an automatic transmission.

In addition, a planetary gear train according to an exemplary embodimentof the present invention may maximize engine driving efficiency bymulti-stages of an automatic transmission, and may improve powerdelivery performance and fuel consumption.

Further, effects that can be obtained or expected from exemplaryembodiments of the present invention are directly or suggestivelydescribed in the following detailed description. That is, variouseffects expected from exemplary embodiments of the present inventionwill be described in the following detailed description.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a planetary gear train according to anexemplary embodiment of the present invention.

FIG. 2 is operational chart for respective control elements atrespective shift stages in a planetary gear train according to anexemplary embodiment of the present invention.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particular intendedapplication and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

The present invention will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. As those skilled in the art would realize,the described embodiments may be modified in various different ways, allwithout departing from the spirit or scope of the present invention.

The drawings and description are to be regarded as illustrative innature and not restrictive, and like reference numerals designate likeelements throughout the specification.

In the following description, dividing names of components into first,second, and the like is to divide the names because the names of thecomponents are the same as each other, and an order thereof is notparticularly limited.

FIG. 1 is a schematic diagram of a planetary gear train according to anexemplary embodiment of the present invention.

Referring to FIG. 1, a planetary gear train according to an exemplaryembodiment of the present invention includes first, second, third, andfourth planetary gear sets PG1, PG2, PG3, and PG4 arranged on a sameaxis, an input shaft IS, an output shaft OS, eight connecting membersTM1 to TM8 for interconnecting rotational elements of the first, second,third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, sixcontrol elements C1 to C3 and B1 to B3, and a transmission housing H.

Torque input from the input shaft IS is shifted by cooperative operationof the first, second, third, and fourth planetary gear sets PG1, PG2,PG3, and PG4, and then output through the output shaft OS.

The simple planetary gear sets are arranged in the order of first,second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4,from an engine side.

The input shaft IS is an input member, and the torque from a crankshaftof an engine, after being torque-converted through a torque converter,is input into the input shaft IS.

The output shaft OS is an output member, and being arranged on a sameaxis with the input shaft IS, delivers a shifted torque to a drive shaftthrough a differential apparatus.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1 thatsupports a first pinion P1 externally engaged with the first sun gearS1, and a first ring gear R1 internally engaged with the first pinionP1. The first sun gear S1 acts as a first rotational element N1, thefirst planet carrier PC1 acts as a second rotational element N2, and thefirst ring gear R1 acts as a third rotational element N3.

The second planetary gear set PG2 is a single pinion planetary gear set,and includes a second sun gear S2, a second planet carrier PC2 thatsupports a second pinion P2 externally engaged with the second sun gearS2, and a second ring gear R2 internally engaged with the second pinionP2. The second sun gear S2 acts as a fourth rotational element N4, thesecond planet carrier PC2 acts as a fifth rotational element N5, and thesecond ring gear R2 acts as a sixth rotational element N6.

The third planetary gear set PG3 is a single pinion planetary gear set,and includes a third sun gear S3, a third planet carrier PC3 thatsupports a third pinion P3 externally engaged with the third sun gearS3, and a third ring gear R3 internally engaged with the third pinionP3. The third sun gear S3 acts as a seventh rotational element N7, thethird planet carrier PC3 acts as an eighth rotational element N8, andthe third ring gear R3 acts as a ninth rotational element N9.

The fourth planetary gear set PG4 is a single pinion planetary gear set,and includes a fourth sun gear S4, a fourth planet carrier PC4 thatsupports a fourth pinion P4 externally engaged with the fourth sun gearS4, and a fourth ring gear R4 internally engaged with the fourth pinionP4. The fourth sun gear S4 acts as a tenth rotational element N10, thefourth planet carrier PC4 acts as an eleventh rotational element N11,and the fourth ring gear R4 acts as a twelfth rotational element N12.

In the arrangement of the first, second, third, and fourth planetarygear sets PG1, PG2, PG3, and PG4, the second rotational element N2 isdirectly connected with the fifth rotational element N5, the sixthrotational element N6 is directly connected with the ninth rotationalelement N9, the seventh rotational element N7 is directly connected withthe tenth rotational element N10, and the eighth rotational element N8is directly connected with the twelfth rotational element N12, by eightconnecting members TM1 to TM8.

The eight connecting members TM1 to TM8 are arranged as follows.

The first connecting member TM1 is connected with the first rotationalelement N1 (first sun gear S1), and directly connected with thetransmission housing H, thereby continuously acting as a fixed element.

The second connecting member TM2 is connected with the second rotationalelement N2 (first planet carrier PC1) and the fifth rotational elementN5 (second planet carrier PC2), and selectively connectable with thetransmission housing H, thereby acting as a selective fixed element.

The third connecting member TM3 is connected with the third rotationalelement N3 (first ring gear R1), and selectively connectable with theinput shaft IS, thereby acting as a selective input element.

The fourth connecting member TM4 is connected with the fourth rotationalelement N4 (second sun gear S2), and directly connected with the inputshaft IS, thereby continuously acting as an input element.

The fifth connecting member TM5 is connected with the sixth rotationalelement N6 (second ring gear R2) and the ninth rotational element N9(third ring gear R3), and selectively connectable with the secondtransmission housing H, thereby acting as a selective fixed element.

The sixth connecting member TM6 is connected with the seventh rotationalelement N7 (third sun gear S3) and the tenth rotational element (N10;fourth sun gear C4), and selectively connectable with the input shaftIS, thereby acting as a selective input element.

The seventh connecting member TM7 is connected with the eighthrotational element N8 (third planet carrier PC3) and the twelfthrotational element N12 (fourth ring gear R4), and selectivelyconnectable with the transmission housing H, thereby acting as aselective fixed element.

The eighth connecting member TM8 is connected with the eleventhrotational element N11 (fourth planet carrier PC4), and connected withthe output shaft OS, thereby continuously acting as an output element.

The connecting members TM1 to TM8 may be selectively interconnected withone another by control elements of three clutches C1, C2, and C3.

The connecting members TM1 to TM8 may be selectively connectable withthe transmission housing H, by control elements of three brakes B1, B2,and B3.

The six control elements C1 to C3 and B1 to B3 are arranged as follows.

The first clutch C1 is arranged between the input shaft IS and the thirdconnecting member TM3, such that the input shaft IS and the thirdconnecting member TM3 may selectively become integral.

The second clutch C2 is arranged between the input shaft IS and thesixth connecting member TM6, such that the input shaft IS and the sixthconnecting member TM6 may selectively become integral.

The third clutch C3 is arranged between the input shaft IS and theseventh connecting member TM7, such that the input shaft IS and theseventh connecting member TM7 may selectively become integral.

The first brake B1 is arranged between the second connecting member TM2and the transmission housing H, such that the second connecting memberTM2 may selectively act as a fixed element.

The second brake B2 is arranged between the fifth connecting member TM5and the transmission housing H, such that the fifth connecting memberTM5 may selectively act as a fixed element.

The third brake B3 is arranged between the seventh connecting member TM7and the transmission housing H, such that the seventh connecting memberTM7 may selectively act as a fixed element.

The control elements of the first, second, third clutches C1, C2, and C3and the first, second, and third brakes B1, B2, and B3 may be realizedas multi-plate hydraulic pressure friction devices that are frictionallyengaged by hydraulic pressure.

FIG. 2 is an operational chart for respective control elements atrespective shift stages in a planetary gear train according to anexemplary embodiment of the present invention.

As shown in FIG. 2, a planetary gear train according to an exemplaryembodiment of the present invention performs shifting by operating twocontrol elements at respective shift stages.

In the first forward speed D1, the first and third brakes B1 and B3 aresimultaneously operated. As a result, torque of the input shaft IS isinput to the fourth connecting member TM4. In addition, while the firstconnecting member TM1 is acting as a fixed element, the third andseventh connecting members TM3 and TM7 act as fixed elements by theoperation of the first and third brakes B1 and B3, thereby realizing thefirst forward speed by cooperative operation of respective connectingmembers and outputting a shifted torque through the output shaft OSconnected with the eighth connecting member TM8.

In the second forward speed D2, the second clutch C2 and the third brakeB3 are simultaneously operated. As a result, the sixth connecting memberTM6 is connected with the input shaft IS by the operation of the secondclutch C2, and torque of the input shaft IS is input to the fourthconnecting member TM4 and the sixth connecting member TM6. In addition,while the first connecting member TM1 is acting as a fixed element, theseventh connecting member TM7 simultaneously acts as a fixed element bythe operation of the third brake B3, thereby realizing the secondforward speed by cooperative operation of respective connecting membersand outputting a shifted torque through the output shaft OS connectedwith the eighth connecting member TM8.

In the third forward speed D3, the second clutch C2 and the first brakeB1 are simultaneously operated. As a result, the sixth connecting memberTM6 is connected with the input shaft IS by the operation of the secondclutch C2, and torque of the input shaft IS is input to the fourthconnecting member TM4 and the sixth connecting member TM6. In addition,while the first connecting member TM1 is acting as a fixed element, thesecond connecting member TM2 simultaneously acts as a fixed element bythe operation of the first brake B1, thereby realizing the third forwardspeed by cooperative operation of respective connecting members andoutputting a shifted torque through the output shaft OS connected withthe eighth connecting member TM8.

In the fourth forward speed D4, the second clutch C2 and the secondbrake B2 are simultaneously operated. As a result, the sixth connectingmember TM6 is connected with the input shaft IS by the operation of thesecond clutch C2, and torque of the input shaft IS is input to thefourth connecting member TM4 and the sixth connecting member TM6. Inaddition, while the first connecting member TM1 is acting as a fixedelement, the fifth connecting member TM5 simultaneously acts as a fixedelement by the operation of the second brake B2, thereby realizing thefourth forward speed by cooperative operation of respective connectingmembers and outputting a shifted torque through the output shaft OSconnected with the eighth connecting member TM8.

In the fifth forward speed D5, the first and second brakes C1 and C2 aresimultaneously operated. As a result, the third connecting member TM3 isconnected with the input shaft IS by the operation of the first clutchC1, and the sixth connecting member TM6 is connected with the inputshaft IS by the operation of the third clutch C3. In this state, torqueof the input shaft IS is input to the third, fourth, and sixthconnecting members TM3, TM4, and TM6. In addition, the first connectingmember TM1 acts as a fixed element, thereby realizing the fifth forwardspeed by cooperative operation of respective connecting members andoutputting a shifted torque through the output shaft OS connected withthe eighth connecting member TM8.

In the sixth forward speed D6, the second and third brakes C2 and C3 aresimultaneously operated. As a result, the sixth connecting member TM6 isconnected with the input shaft IS by the operation of the second clutchC2, and the seventh connecting member TM7 is connected with the inputshaft IS by the operation of the third clutch C3. In this state, torqueof the input shaft IS is input to the fourth, sixth, and seventhconnecting members TM4, TM6, and TM7. Then, the third and fourthplanetary gear sets PG3 and PG4 integrally rotate at a same speed withthe input shaft IS, thereby realizing the sixth forward speed andoutputting a same torque as inputted through the output shaft OSconnected with the eighth connecting member TM8.

In the seventh forward speed D7, the first and third brakes C1 and C3are simultaneously operated. As a result, the third connecting memberTM3 is connected with the input shaft IS by the operation of the firstclutch C1, and the seventh connecting member TM7 is connected with theinput shaft IS by the operation of the third clutch C3. In this state,torque of the input shaft IS is input to the third, fourth, and seventhconnecting members TM3, TM4, and TM7. In addition, the first connectingmember TM1 acts as a fixed element, thereby realizing the seventhforward speed by cooperative operation of respective connecting membersand outputting a shifted torque through the output shaft OS connectedwith the eighth connecting member TM8.

In the eighth forward speed D8, the third clutch C3 and the second brakeB2 are simultaneously operated. As a result, the seventh connectingmember TM7 is connected with the input shaft IS by the operation of thethird clutch C3, and torque of the input shaft IS is input to the fourthand seventh connecting members TM4 and TM7. In addition, while the firstconnecting member TM1 is acting as a fixed element, the fifth connectingmember TM5 simultaneously acts as a fixed element by the operation ofthe second brake B2, thereby realizing the eighth forward speed bycooperative operation of respective connecting members and outputting ashifted torque through the output shaft OS connected with the eighthconnecting member TM8.

In the ninth forward speed D9, the third clutch C3 and the first brakeB1 are simultaneously operated. As a result, the seventh connectingmember TM7 is connected with the input shaft IS by the operation of thethird clutch C3, and torque of the input shaft IS is input to the fourthand seventh connecting members TM4 and TM7. In addition, while the firstconnecting member TM1 is acting as a fixed element, the secondconnecting member TM2 simultaneously acts as a fixed element by theoperation of the first brake B1, thereby realizing the ninth forwardspeed by cooperative operation of respective connecting members andoutputting a shifted torque through the output shaft OS connected withthe eighth connecting member TM8.

In the reverse speed REV, the first clutch C1 and the third brake B3 aresimultaneously operated. As a result, the third connecting member TM3 isconnected with the input shaft IS by the operation of the first clutchC1, and torque of the input shaft IS is input to the third and fourthconnecting members TM3 and TM4. In addition, while the first connectingmember TM1 is acting as a fixed element, the seventh connecting memberTM7 simultaneously acts as a fixed element by the operation of the thirdbrake B3, thereby realizing the reverse speed by cooperation operationof respective connecting members and outputting a shifted torque throughthe output shaft OS connected with the eighth connecting member TM8.

As described above, a planetary gear train according to an exemplaryembodiment of the present invention may realize at least nine forwardspeeds and at least one reverse speed formed by operating the fourplanetary gear sets PG1, PG2, PG3, and PG4 by controlling the threeclutches C1, C2, and C3 and the three brakes B1, B2, and B3.

In addition, a planetary gear train according to an exemplary embodimentof the present invention may substantially improve driving stability byrealizing shift stages appropriate for rotation speed of an engine dueto multi-stages of an automatic transmission.

In addition, a planetary gear train according to an exemplary embodimentof the present invention may maximize engine driving efficiency bymulti-stages of an automatic transmission, and may improve powerdelivery performance and fuel consumption.

For convenience in explanation and accurate definition in the appendedclaims, the terms “upper”, “lower”, “inner” and “outer” are used todescribe features of the exemplary embodiments with reference to thepositions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described in orderto explain certain principles of the invention and their practicalapplication, to thereby enable others skilled in the art to make andutilize various exemplary embodiments of the present invention, as wellas various alternatives and modifications thereof. It is intended thatthe scope of the invention be defined by the Claims appended hereto andtheir equivalents.

What is claimed is:
 1. A planetary gear train of an automatictransmission for a vehicle, comprising: an input shaft configured forreceiving an engine torque; an output shaft configured for outputting ashifted torque; a first planetary gear set having first, second, andthird rotation elements; a second planetary gear set having fourth,fifth, and sixth rotation elements; a third planetary gear set havingseventh, eighth, and ninth rotation elements; a fourth planetary gearset having tenth, eleventh, and twelfth rotation elements; six controlelements for selectively interconnecting the first, second, third,fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, andtwelfth rotation elements and a transmission housing; a first connectingmember connected with the first rotation element and directly connectedwith the transmission housing; a second connecting member connected withthe second rotation element and the fifth rotation element, andselectively connectable with the transmission housing; a thirdconnecting member connected with the third rotation element, andselectively connectable with the input shaft; a fourth connecting memberconnected with the fourth rotation element and directly connected withthe input shaft; a fifth connecting member connected with the sixthrotation element and the ninth rotation element, and selectivelyconnectable with the transmission housing; a sixth connecting memberconnected with the seventh rotation element and the tenth rotationelement, and selectively connectable with the input shaft; a seventhconnecting member connected with the eighth rotation element and thetwelfth rotation element, and selectively connectable with thetransmission housing; and an eighth connecting member connected with theeleventh rotation element and directly connected with the output shaft.2. The planetary gear train of claim 1, wherein the first planetary gearset is a single pinion planetary gear set, where the first rotationelement is a first sun gear, the second rotation element is a firstplanet carrier, and the third rotation element is a first ring gear; thesecond planetary gear set is a single pinion planetary gear set, wherethe fourth rotation element is a second sun gear, the fifth rotationelement is a second planet carrier, and the sixth rotation element is asecond ring gear; the third planetary gear set is a single pinionplanetary gear set, where the seventh rotation element is a third sungear, the eighth rotation element is a third planet carrier, and theninth rotation element is a third ring gear; and the fourth planetarygear set is a single pinion planetary gear set, where the tenth rotationelement is a fourth sun gear, the eleventh rotation element is a fourthplanet carrier, and the twelfth rotation element is a fourth ring gear.3. The planetary gear train of claim 1, wherein the six control elementscomprise: a first clutch selectively connecting the input shaft and thethird connecting member; a second clutch selectively connecting theinput shaft and the sixth connecting member; a third clutch selectivelyconnecting the input shaft and the seventh connecting member; a firstbrake selectively connecting the second connecting member and thetransmission housing; a second brake selectively connecting the fifthconnecting member and the transmission housing; and a third brakeselectively connecting the seventh connecting member and thetransmission housing.
 4. The planetary gear train of claim 3, whereinshift stages realized by selective operation of two control elements ofthe six control elements comprise: a first forward speed formed bysimultaneous operation of the first and third brakes; a second forwardspeed formed by simultaneous operation of the second clutch and thethird brake; a third forward speed formed by simultaneous operation ofthe second clutch and the first brake; a fourth forward speed formed bysimultaneous operation of the second clutch and the second brake; afifth forward speed formed by simultaneous operation of the first andsecond clutches; a sixth forward speed formed by simultaneous operationof the second and third clutches; a seventh forward speed formed bysimultaneous operation of the first and third clutches; an eighthforward speed formed by simultaneous operation of the third clutch andthe second brake; a ninth forward speed formed by simultaneous operationof the third clutch and the first brake; and a reverse speed formed bysimultaneous operation of the first clutch and the third brake.
 5. Aplanetary gear train of an automatic transmission for a vehicle,comprising: an input shaft configured for receiving an engine torque; anoutput shaft configured for outputting a shifted torque; a firstplanetary gear set as a single pinion planetary gear set having first,second, and third rotation elements; a second planetary gear set as asingle pinion planetary gear set having fourth, fifth, and sixthrotation elements; a third planetary gear set as a single pinionplanetary gear set having seventh, eighth, and ninth rotation elements;a fourth planetary gear set as a single pinion planetary gear set havingtenth, eleventh, and twelfth rotation elements; a first connectingmember connected with the first rotation element and directly connectedwith a transmission housing; a second connecting member connected withthe second rotation element and the fifth rotation element, andselectively connectable with the transmission housing; a thirdconnecting member connected with the third rotation element, andselectively connectable with the input shaft; a fourth connecting memberconnected with the fourth rotation element and directly connected withthe input shaft; a fifth connecting member connected with the sixthrotation element and the ninth rotation element, and selectivelyconnectable with the transmission housing; a sixth connecting memberconnected with the seventh rotation element and the tenth rotationelement, and selectively connectable with the input shaft; a seventhconnecting member connected with the eighth rotation element and thetwelfth rotation element, and selectively connectable with thetransmission housing; an eighth connecting member connected with theeleventh rotation element and directly connected with the output shaft;a first clutch selectively connecting the input shaft and the thirdconnecting member; a second clutch selectively connecting the inputshaft and the sixth connecting member; a third clutch selectivelyconnecting the input shaft and the seventh connecting member; a firstbrake selectively connecting the second connecting member and thetransmission housing; a second brake selectively connecting the fifthconnecting member and the transmission housing; and a third brakeselectively connecting the seventh connecting member and thetransmission housing.
 6. The planetary gear train of claim 5, whereinthe first planetary gear set includes a first sun gear as the firstrotation element, a first planet carrier as the second rotation element,and a first ring gear as the third rotation element; the secondplanetary gear set includes a second sun gear as the fourth rotationelement, a second planet carrier as the fifth rotation element, and asecond ring gear as the sixth rotation element; the third planetary gearset includes a third sun gear as the seventh rotation element, a thirdplanet carrier as the eighth rotation element, and a third ring gear asthe ninth rotation element; and the fourth planetary gear set includes afourth sun gear as the tenth rotation element, a fourth planet carrieras the eleventh rotation element, and a fourth ring gear as the twelfthrotation element.
 7. The planetary gear train of claim 5, wherein shiftstages realized by selective operation of two control elements among thesix control elements of the three clutches and the three brakescomprise: a first forward speed formed by simultaneous operation of thefirst and third brakes; a second forward speed formed by simultaneousoperation of the second clutch and the third brake; a third forwardspeed formed by simultaneous operation of the second clutch and thefirst brake; a fourth forward speed formed by simultaneous operation ofthe second clutch and the second brake; a fifth forward speed formed bysimultaneous operation of the first and second clutches; a sixth forwardspeed formed by simultaneous operation of the second and third clutches;a seventh forward speed formed by simultaneous operation of the firstand third clutches; an eighth forward speed formed by simultaneousoperation of the third clutch and the second brake; a ninth forwardspeed formed by simultaneous operation of the third clutch and the firstbrake; and a reverse speed formed by simultaneous operation of the firstclutch and the third brake.
 8. A planetary gear train of an automatictransmission for a vehicle, comprising: an input shaft configured forreceiving an engine torque; an output shaft configured for outputting ashifted torque; a first planetary gear set as a single pinion planetarygear set having a first sun gear, a first planet carrier, and a firstring gear; a second planetary gear set as a single pinion planetary gearset having a second sun gear, a second planet carrier, and a second ringgear; a third planetary gear set as a single pinion planetary gear sethaving a third sun gear, a third planet carrier, and a third ring gear;a fourth planetary gear set as a single pinion planetary gear set havinga fourth sun gear, a fourth planet carrier, and a fourth ring gear; afirst connecting member connected with the first sun gear, and directlyconnected with a transmission housing; a second connecting memberconnected with the first planet carrier and the second planet carrier,and selectively connectable with the transmission housing; a thirdconnecting member connected with the first ring gear, and selectivelyconnectable with the input shaft; a fourth connecting member connectedwith the second sun gear and directly connected with the input shaft; afifth connecting member connected with the second ring gear and thethird ring gear, and selectively connectable with the transmissionhousing; a sixth connecting member connected with the third sun gear andthe fourth sun gear, and selectively connectable with the input shaft; aseventh connecting member connected with the third planet carrier andthe fourth ring gear, and selectively connectable with the transmissionhousing; an eighth connecting member connected with the fourth planetcarrier, and directly connected with the output shaft; and six controlelements selectively connecting the first, second, third, fourth, fifth,sixth, seventh, and eighth connecting members and the transmissionhousing.
 9. The planetary gear train of claim 8, wherein the six controlelements comprise: a first clutch selectively connecting the input shaftand the third connecting member; a second clutch selectively connectingthe input shaft and the sixth connecting member; a third clutchselectively connecting the input shaft and the seventh connectingmember; a first brake selectively connecting the second connectingmember and the transmission housing; a second brake selectivelyconnecting the fifth connecting member and the transmission housing; anda third brake selectively connecting the seventh connecting member andthe transmission housing.
 10. The planetary gear train of claim 9,wherein shift stages realized by selective operation of two controlelements of the six control elements comprise: a first forward speedformed by simultaneous operation of the first and third brakes; a secondforward speed formed by simultaneous operation of the second clutch andthe third brake; a third forward speed formed by simultaneous operationof the second clutch and the first brake; a fourth forward speed formedby simultaneous operation of the second clutch and the second brake; afifth forward speed formed by simultaneous operation of the first andsecond clutches; a sixth forward speed formed by simultaneous operationof the second and third clutches; a seventh forward speed formed bysimultaneous operation of the first and third clutches; an eighthforward speed formed by simultaneous operation of the third clutch andthe second brake; a ninth forward speed formed by simultaneous operationof the third clutch and the first brake; and a reverse speed formed bysimultaneous operation of the first clutch and the third brake.